1. Field of the Invention
The present invention relates to suppression, if not prevention, of exhaust gas combustion in a multiple rocket exhaust plenum. More particularly, the present invention relates to a system for providing controlled flow of inert gases to a rocket exhaust plenum to prevent intake of oxygen which renders the exhaust mixture combustible.
2. Description of the Prior Art
For military applications rockets, missiles or other exhaust-gas propelled vehicles are often stored in closely adjacent magazines, chambers or launch tubes. In these cases, exhaust gas ducts are normally provided to convey rocket exhaust gases generated during rocket ignition to a safe location. Where available space is at a premium, as for example on board ship, manifolding of a number of closely adjacent launch tubes or chambers into a common exhaust manifold or plenum chamber is often necessary.
Various problems may develop if ducts connecting launch tubes to a common exhaust manifold are normally open before launch of the vehicles. If one or more of the rockets is intentionally or accidentally ignited, portions of the resulting exhaust gases, which may have temperatures as high as 6,000.degree. F., can be circulated through the common manifold, into the connecting ducts and into other launch chambers. This could ignite other rockets. Also, the warheads in the launch chambers could be detonated by these hot gases. At a minimum, the gases could damage the rocket, associated equipment and hold-down devices. Thus accidental or intentional ignition of one rocket could render a whole ship or launching system ineffective. In addition, if the some of the launch tubes are open at their upper ends, exhaust gases entering the chambers through the connecting ducts could escape through the open outer ends.
More importantly, when a rocket is launched from a multiple rocket canister with a common plenum, a fuel rich exhaust gas mixture containing hydrogen and carbon monoxide is present in the empty launch tube and plenum. This can present a potential explosion hazard if air containing oxygen, e.g. from the atmosphere, is mixed into the system prior to the next rocket launch. Since these exhaust gas residuals are initially quite hot, up to 6,000.degree. F. as noted, cool-down will naturally occur in the interval following launch and the internal pressure of the system will decrease. Even after the system is closed following the launch, it contains hot residual exhaust gases and other outgases from the system components, for example ablative materials, which are rich in hydrocarbons, carbon monoxide and hydrogen. As the pressure decreases external air can be drawn into the system, for instance, through the launch tube of the next launched rocket since it must be uncovered in order to allow the rocket to be launched. Thus, a system for preventing production of combustible mixtures in the plenum and in empty rocket launch tubes is needed.
The prior art discloses many different systems for utilizing a single plenum for the multiple firing of rockets from tubes. For instance, U.S. Pat. Nos. 4,044,648, 4,134,327 and 4,173,919 of the inventor herein all disclose systems utilizing a common exhaust duct to discharge exhaust gases produced by the firing of multiple rockets.
The need to detect fires and provides a means to control them is recognized in U.S. Pat. No. 3,052,303 of Lapp which discloses a system to extinguish inadvertently ignited rockets in a storage area by utilizing the pressure produced by the rocket exhaust to open a clapper valve and force water into the rocket's chamber until the ignition is extinguished. Glendinning et al. in U.S. Pat. No. 2,693,240 disclose another system to detect an explosion in aircraft during its initial phase and suppress the explosion by use of fire extinguishers.
It is also known in the prior art to utilize recirculated combustion exhaust materials, which are relatively inert, in order to provide a noncombustible atmosphere in closed containers. For instance, see U.S. Pat. Nos. 2,756,215 of Burgess et al. and 3,103,296 of Gour.
In another area of art, numerous patents have been issued which deal with methods of extinguishing fires or suppressing combustion after a fire has been initiated. Generally, these methods deal with the dilution of available air using some inert gas delivery method. For example, the following references are of interest: U.S. Pat. Nos. 649,923 of Febiger, 1,312,224 of Wotherspoon, 1,993,695 of Allen et al., 2,050,687 of Allen, 2,543,362 of Getz, 3,468,562 of Goodloe et al., 3,830,307 of Bragg et al. and 3,893,514 of Carhart et al.